1. Field of the Invention
This invention relates to a method of aligning a record of sample data with a record of reference data. In a particular aspect, the present invention relates to a method of aligning a time record of sample data with a time record of reference data. Another aspect of the invention relates to a method of aligning the signals of a sample mass chromatogram with the signals of a reference mass chromatogram, and more particularly to a method of aligning signals of a sample chromatogram to signals of a primary standard chromatogram using a secondary standard chromatogram which includes signals corresponding to signals of the primary standard chromatogram but located at different times therefrom. Another aspect of the present invention relates to a method of analyzing a sample substance using mass chromatograms in which constituents of substances are designated by signals aligned to time designations, and more specifically it relates to a method of comparing at least two unknown hydrocarbon-bearing substances. Another aspect of the present invention includes a method of reservoir analysis for one or more subterranean fluid-containing reservoirs. Still another aspect of the present invention includes a method of aligning sample records so that the aligned sample records define a database on which a meaningful statistical analysis can be performed, wherein the sample records are gas chromatography/mass spectrometry (GC/MS) constituent peak-time records for a plurality of samples.
2. Setting of the Invention
One technique for analyzing a substance, such as crude oil or a rock extract taken from an oil well, is to process the substance through gas chromatography/mass spectrometry (GC/MS) equipment. This equipment detects the presence of different constituents or components of the substance which have, or are given, net electric charges. These electrically charged constituents may be referred to as fragments having respective mass-per-charge (m/z) values. For each constituent or fragment detected, a respective graph or collection of data, called an ion chromatogram or mass chromatogram, is produced. Each chromatogram shows intensity or quantitative data of a particular m/z fragment versus its time of detection, given as a scan number or a retention time. The intensity or quantity is a distinct or distinguishable feature or characteristic, and it is graphically represented by a peak signal. Usually, only a small portion of the total time of a chromatogram is of interest for a particular m/z profile. The region containing useful information for a given m/z is called a time window or window-of-interest.
Ideally, detection of the same m/z fragment at two different processing times would produce the same chromatogram so that direct comparisons could be made to analyze an unknown mixture relative to a known substance. Thus, for example, analyses of unknown crude oils or rock extracts could be made in the oil and gas industry, or aligned databases could be available for accurate statistical analysis. Unfortunately, data, as taken directly from GC/MS equipment, do not meet this ideal. Flow changes, procedure temperature variations, column aging, etc., contribute to later taken chromatograms typically being offset time-wise from earlier taken chromatograms. This deficiency has been known, and proposals regarding alignment or correlation of one chromatogram to another have been made. See U.S. Pat. No. 3,898,837 to Boege; J. A. Pino et al., "Application of Pyrolysis/Gas Chromatography/Pattern Recognition to the Detection of Cystic Fibrosis Heterozygotes," Analytical Chemistry, Vol. 57, No. 1, pp. 295-302 (January, 1985); M. E. Parrish et al., "Computer-Enhanced High-Resolution Gas Chromatography for the Discriminative Analysis of Tobacco Smoke," Analytical Chemistry, Vol. 53, No. 6, pp. 826-831 (May, 1981).
Because of the time offset which can result between one chromatogram and another when two are taken at substantially different times, there is the need for a method by which a mass chromatogram for an unknown sample can be aligned, preferably automatically, with a reference mass chromatogram regardless, at least initially, of differences or similarities between the two chromatograms. That is, there is the need for a method which can align two chromatograms even when they appear to be widely divergent, such as due to the peak signals of one chromatogram not being within a typical tolerance which may have been suggested in prior types of alignment or correlation techniques or such as due to the absence of one or more of the peak signals in one of the chromatograms. Satisfying these needs would be useful in providing an improved method of analyzing a sample substance using mass chromatograms and particularly a method of comparing at least two unknown hydrocarbon-bearing substances. Satisfying these needs would also be useful in implementing a method of reservoir analysis for one or more subterranean fluid-containing reservoirs and in a method of aligning sample records so that the aligned sample records define a database on which a meaningful statistical analysis can be performed.